CBN ⇝

call-by-name

(CBN) (Normal order reduction, leftmost, outermost
reduction). An argument passing convention (first provided
by ALGOL 60?) where argument expressions are passed
unevaluated. This is usually implemented by passing a pointer
to a thunk - some code which will return the value of the
argument and an environment giving the values of its free
variables.

The opposite of call-by-name is call-by-value where
arguments are evaluated before they are passed to a function.
This is more efficient but is less likely to terminate in the
presence of infinite data structures and recursive
functions.